When formed bodies having predetermined shapes are formed, a method is generally used in which dies including openings having the predetermined shapes are attached to a tip of an extruder to perform extrusion forming, but the openings of the dies are sometimes clogged with foreign matters, hard soil and the like, and the dies need to be periodically cleaned. Especially when formed bodies having structures including a large number of thin ribs, such as honeycomb structures, are formed, the dies include fine slits for forming the ribs, space portions such as the fine slits are easily clogged with the foreign matters, and the foreign matters are not easily removed.
As a forming-material for use in this forming, clay obtained by adding an organic binder and the like to particulate matters such as ceramic and metal is generally used. Therefore, when the dies for use in the forming using the clay as a raw material are cleaned, the space portions of the dies are mainly clogged with the clay, and the clay needs to be removed. To clean the dies, for example, a washing method by high-pressure water and the like are used, but when the die has a complicated structure or a material of the die is brittle, defects such as breakage and deformation are easily generated at the time of the washing at a high pressure. The defects are easily generated especially in the die having a structure including a large number of fine slits. There has also been a problem that the die cannot be sufficiently cleaned, when the pressure of washing water is lowered in order to prevent the defects. Therefore, there has been a demand for a die cleaning method in which defects at the time of cleaning are not easily generated and a die can be sufficiently cleaned.